Electric and hybrid vehicles may have one or more high voltage buses that are isolated from the chassis, Earth ground, or both, of the vehicle during normal operation. A hybrid vehicle may comprise an internal combustion engine that rotates a generator rotor or an alternator rotor to provide electrical energy for one or more electric drive motors to propel the vehicle. However, if an electrical short or another electrical problem occurs in vehicle circuitry or electromechanical devices on the vehicle, one or more high voltage buses may apply undesired electrical energy to the vehicle chassis, which can detract from vehicle performance or pose safety concerns. Thus, there is need to detect degraded electrical isolation between one or more high voltage buses and the chassis or Earth ground of the vehicle. Further, there is need to identify the source or location of the electrical problem on the vehicle.